Thestrongestathletescanliftcloseto455kgjustofftheground,butfewordinarypeoplecanliftmorethanabout68kg.Earlymansoondevelopedmachinesforliftinglargestonesandtreetrunks.Asimpledeviceisasinglepulleywheelarrangedasahoist.Butaropearoundonepulleymerelychangesthed (共 5981 字) [閱讀本文] >>